Comportamento de bovinos de corte e o microclima em sistemas silvipastoris com eucaliptos

Abstract

The objective ofthis work was to evaluate if the presence oftrees and its height in silvipastorai systems modi& the microclimate, the environment and the bovine intake behavior during the day in the summer. Jt was evaluate the microclimate of the e environment in fomed silvipastoral systems with rank of eucaiyptus with 8 (SSP8), 18 (SSP1 8) and 28 (SSP28) meters ofheight, confpared with a system without trees (WT) in the sunnner. The experimental design was a split splot, with six time in the sub parceis, having in the systems the parceis and the months as blocks in four replications and the interaction hourly x system. The air temperature (Ta), biack globe temperature (Bt), relative humidity (RH) and wind speed (WS) were observed to create the thermai comfort index: temperature..humidity index (THJ); black globe-humidity index (BGHJ); heat load index (HLJ) and the radiant thennal ioad index (RTL). With exception of the UR there was interaction for houriy x system for ali variables and indexes. Interaction occurred for: Ta at 10 and 18 hours; Vv from 8 to 16 hours; THI at 10 and 12 hours; Bt, BGHI, HLJ and RTL in ali times. In the summer, the system with shade SSP28 had the iowest average of Bt, WS, BGHI, RTL and HLJ. There was a reductjon of WS average in systems SSP8, SSP18 and SSP28 in, respectively, 20.7; 50.0 and 48.0% in reiation to WT system, however it was not proportionai to the height, with influence of the rank porosity and pantries height . However for RTL the reduction was proportional to the height of the trees with 10.24; 12.49 and 20.76%, respectively, for SSP8, SSPI8 and SSP28. There was a reduction of the stress thermal in the environment by trees presence, being the HLI the index that better demonstrated the effect, however not proportionai to the rank height . For the intake behavior of Nellore heifers it was used 30 animais distributed in a system without shade (SS), with trees with eight meters (SSP8) and 18 m (SSPJ8). The data were coliected in 3 days for 12 hours, subdivided in; P1 (7: 15 to the 13:00 hours) and P2 (13: 15 to the 19:00 hours). There were evaiuated the times and frequency of grazing, rumination, idie and the percentage of time that the animais had remained at shade. The average and minimum values of the index of temperature from the globe-humjdjty were lower and equal (86 and 82) for SSP8 and SSPI 8 than for SS (89 and 86). There was interaction between the systems and the periods for ali the anaiyzed variabie, with exception ofthe rumination frequency (RUF). For system WS the grazing time (GT) did not differ (p>0.05) between P1 (202 mm) and P2 (187 mi, however the grazing frequency (GFR) was iower for P2 (3.17). For systems SSP8 and SSP18 the GT in the P2, respectiveiy, with 195.50 and 219.00 mm. was higher (p<0.05) than in the P1, respectiveiy, with 128.00 and 158.50 mi The rumination time (RUT) was higher in the P1 for ali systems. The GFR was for SSP8 with 3.58, SS with 3.05 and SSPi8 with 2.22. A higher idie time (IT) and the idle frequency (IF) had been found in system SS (97.50 mm and 3.80 respectiveiy) in the P2, being for systems SSP8 (98.50 mm and 4.47 respectively) and SSPI8 (127.00 mm and 4.27 respectiveiy) were higher in the P1 (p<0.05). The animais in SSP8 and SSP18 had passed on average 43.49 and 49.81% respectiveiy of the time in the shade. It was conciuded that the presence of trees in the SSP modified between P1 and the P2 the GT and IT and GFR and JF ofthe animais, however, it did not influence RUT and RUF.